Recently, with electronic products developing towards precision and versatility, the chip structure of integrated circuits used in electronic products tends to be complicated. At the time of manufacture, in order to ensure the electrical quality of the wafer, wafer-level measurement is performed before packaging the wafer. The current measuring method for testing wafers needs a probe card. According to the type of probes, probe card type includes a cantilever probe card and a vertical probe card. In use, the probes of the probe card are directly electrically contacted with pads or bumps of the wafer, and then an electrical signal is transmitted into a tester through a circuit board of the probe card, such that a testing signal from the tester is transmitted into the wafer, or an output signal from the wafer can be received by the tester, thereby achieving the measurement of the electrical properties of the wafer. Moreover, the user can remove a bad wafer according to the measurement results, so as to save unnecessary packaging costs.
FIG. 1 depicts a structural diagram of a spring probe 10 in the prior art. The spring probe 10 includes a probe head 11 and an elastic element 12. A terminal of the elastic element 12 is welded with the probe head 11, and the other terminal of the elastic element 12 is used for assembling with a probe card. FIG. 2 depicts another structural diagram of a spring probe 20 in the prior art. The spring probe 20 includes a probe head 21, an elastic element 22, and a probe tail 23. The spring probe 20 is roughly similar to the spring probe 10, and the difference between them are that two terminals of the elastic element 22 of the spring probe 20 are welded with the probe head 21 and the probe tail 23, respectively, and another terminal of the probe tail 23 is used for assembling with a probe card. Furthermore, the spring probe 20 may include a position sleeve (not shown in the drawing), which is sleeved onto the elastic element 22 for limiting the elastic element 22 to move forward and back in a straight line, thereby ensuring that there is no traverse movement in the corresponding position of the probe head 21 and the probe tail 23.
When measured by the conventional spring probe 10 or 20, the probe head 11 or 21 is firstly aligned with a pad or a bump of the wafer, and then pressure is applied to the spring probe 10 or 20 to ensure that the probe head 11 or 21 is effectively in electrical contact with the wafer, thereby transmitting current through the spring probe 10 or 20. That is, the current must be transmitted through the elastic element 12 or 22. However, in order to ensure the elastic deformation ability of the elastic element 12 or 22, the elastic material of the elastic element 12 or 22 must have a small cross-section area. Thus, if the current exceeds the maximum withstand current of the elastic elements 12 and 22, the elastic elements 12 and 22 may be deformed due to overheating that results in the so-called “needle burning”. On the other hand, when the spring probes 10 and 20 perform high-speed signal transmission, since the transmission path of the elastic elements 12 and 22 is too long, an inductance effect is likely to occur, thereby affecting the signal quality.
Accordingly, it is necessary to provide an improved probe structure to solve the technical problem in the prior art.